function out = L2Proj( y )
[M N] = size(y);
N = N/2;
p = zeros(M,N);
p = sqrt(y(1:M, 1:N).^2 + y(1:M,N+1:2*N).^2);
p = repmat(p,[1,2]);
J = ones(M,N*2);
out = y./ max(p, J);
end